Technical Field
The present invention relates to a device for detecting an open phase in a connection line of a standby transformer in a nuclear power plant using a Rogowski coil.
Background Art
There are not known inventions related to a system for detecting an open phase in a connection line of a transformer yet.
Recently, an open phase is generated due to damage of an insulator of a phase ‘C’ supporting a primary transmission line of a standby transformer during a normal operation in United States Byron nuclear power plant so that a nuclear reactor is finally stopped. Transient phenomenon occurs for about 8 minutes 2 times due to unbalance degree of power phase in a power plant.
US Nuclear Regulatory Commission reports that similar symptoms are experienced in other power plants from the investigation result.
In the US NRC, with respect to operating nuclear power plants, nuclear power plants under construction as well as the atmospheric models of phase transformers of final design (Design Certification), there is a need to establish a system capable of detecting an open phase of power lines connected to a standby transformer. There is a high probability where Korea Institute of Nuclear Safety (KINS: Korea Institute of Nuclear Safety) requests to establish measures, such as the United States in the future.
A transformer protection relay system in Nuclear power stations which is currently used includes low-voltage relays, overcurrent relays, and differential relays, etc. to be operated. However, the open shape is generated in a connection line of a standby transformer, the transformer protection relay system cannot detect the generation of the open phase. Especially in the case of the standby transformer, when a secondary side is disconnected (open) upon a normal operation so that the open phase is generated in the primary line, it is impossible to detect the generation of the open phase. Furthermore, failure of an off-site electrical system spreads to a power system in a safety rating power plant so that problems such as damage of a power device or shutdown of a nuclear reactor may occur.